The flow in the positive displacement blower is very complex.The existing two-dimensional numerical simulation cannot provide the detailed flow information,especially flow characteristics along the axial direction,whi...The flow in the positive displacement blower is very complex.The existing two-dimensional numerical simulation cannot provide the detailed flow information,especially flow characteristics along the axial direction,which is unfavorable to improve the performance of positive displacement blower.To investigate the effects of spiral inlet and outlet on the aerodynamic performance of positive displacement blower,three-dimensional unsteady flow characteristics in a three-lobe positive displacement blower with and without the spiral inlet and outlet are simulated by solving Navier-Stokes equations coupled with RNG k-ε turbulent model.In the numerical simulation,the dynamic mesh technique and overset mesh updating method are used.The computational results are compared with the experimental measurements on the variation of flow rate with the outlet pressure to verify the validity of the numerical method presented.The results show that the mass flow rate with the change of pressure is slightly affected by the application of spiral inlet and outlet,but the internal flow state is largely affected.In the exhaust region,the fluctuations of pressure,velocity and temperature as well as the average values of velocity are significantly reduced.This illustrates that the spiral outlet can effectively suppress the fluctuations of pressure,thus reducing reflux shock and energy dissipation.In the intake area,the average value of pressure,velocity and temperature are slightly declined,but the fluctuations of them are significantly reduced,indicating that the spiral inlet plays the role in making the flow more stable.The numerical results obtained reveal the three-dimensional flow characteristics of the positive displacement blower with spiral inlet and outlet,and provide useful reference to improve performance and empirical correction in the noise-reduction design of the positive displacement blowers.展开更多
As a new structure of solid matter quasicrystal brings profound new ideas to the traditional condensed matter physics, its elastic equations are more complicated than that of traditional crystal. A contact problem of ...As a new structure of solid matter quasicrystal brings profound new ideas to the traditional condensed matter physics, its elastic equations are more complicated than that of traditional crystal. A contact problem of decagonal two? dimensional quasicrystal material under the action of a rigid flat die is solved satisfactorily by introducing displacement function and using Fourier analysis and dual integral equations theory, and the analytical expressions of stress and displacement fields of the contact problem are achieved. The results show that if the contact displacement is a constant in the contact zone, the vertical contact stress has order -1/2 singularity on the edge of contact zone, which provides the important mechanics parameter for contact deformation of the quasicrystal.展开更多
The interface crack problems in the two-dimensional(2D)decagonal quasicrystal(QC)coating are theoretically and numerically investigated with a displacement discontinuity method.The 2D general solution is obtained base...The interface crack problems in the two-dimensional(2D)decagonal quasicrystal(QC)coating are theoretically and numerically investigated with a displacement discontinuity method.The 2D general solution is obtained based on the potential theory.An analogy method is proposed based on the relationship between the general solutions for 2D decagonal and one-dimensional(1D)hexagonal QCs.According to the analogy method,the fundamental solutions of concentrated point phonon displacement discontinuities are obtained on the interface.By using the superposition principle,the hypersingular boundary integral-differential equations in terms of displacement discontinuities are determined for a line interface crack.Further,Green’s functions are found for uniform displacement discontinuities on a line element.The oscillatory singularity near a crack tip is eliminated by adopting the Gaussian distribution to approximate the delta function.The stress intensity factors(SIFs)with ordinary singularity and the energy release rate(ERR)are derived.Finally,a boundary element method is put forward to investigate the effects of different factors on the fracture.展开更多
For compressible two-phase displacement problem, a kind of upwind operator splitting finite difference schemes is put forward and make use of operator splitting, of calculus of variations, multiplicative commutation r...For compressible two-phase displacement problem, a kind of upwind operator splitting finite difference schemes is put forward and make use of operator splitting, of calculus of variations, multiplicative commutation rule of difference operators, decomposition of high order difference operators and prior estimates are adopted. Optimal order estimates in L 2 norm are derived to determine the error, in the approximate solution.展开更多
Differential synthetic aperture radar interferometry (D-InSAR) can only measure one-dimensional surface displacements along the line-of-sight (LOS) direction which greatly inhibits its development and application.In t...Differential synthetic aperture radar interferometry (D-InSAR) can only measure one-dimensional surface displacements along the line-of-sight (LOS) direction which greatly inhibits its development and application.In this paper, we introduce a novel approach to measuring two-dimensional (2-D) surface displacements by exploiting a single InSAR pair, which is called multi-aperture InSAR (MAI) technology.We study the effects of baseline errors and the ionosphere on MAI technology and develop a directional filter and interpolator to minimize the ionospheric effects.A PALSAR image pair covering the 2010 Yushu earthquake is used to estimate the 2-D displacement fields of the earthquake using the MAI approach.The experimental results show that MAI is superior to conventional Offset-Tracking and therefore has great potential in co-seismic displacement measurement and source parameter inversion.展开更多
Based on new rolling-sliding compound bearings,the wear between the one-way spiral hollow cylindrical roller and the ribs of the inner and outer ring of rolling-sliding compound bearings is reduced by innovational str...Based on new rolling-sliding compound bearings,the wear between the one-way spiral hollow cylindrical roller and the ribs of the inner and outer ring of rolling-sliding compound bearings is reduced by innovational structural design. A new left-right spiral hollow cylindrical roller is proposed to replace the one-way spiral hollow cylindrical roller. The finite element analysis models of ordinary cylindrical rollers,one-way spiral hollow cylindrical rollers and left-right spiral hollow cylindrical rollers are respectively established by ABAQUS.The axial displacement of their center mass and the stress distribution of left-right spiral hollow cylindrical rollers are compared and analyzed. Theoretical study results show that this new left-right spiral hollow cylindrical roller not only inherits the advantages of one-way spiral hollow cylindrical rollers,but also avoids the axial offset and the serious wear of the one-way spiral hollow cylindrical roller. And the theory research conclusion is verified by the experiment. The left-right spiral hollow cylindrical roller has the advantages to overcome boundary stress concentration like logarithmic convex roller. The rolling-sliding compound bearings equipped with the new rollers can be better to adapt to the impact of vibration load.展开更多
基金supported by Fundamental Research Funds for the Central UniversitiesChina(Grant No.xjj20100073)Science and Technology Innovation Project of Shaanxi Province of China(Grant No.2011KTCL01-04)
文摘The flow in the positive displacement blower is very complex.The existing two-dimensional numerical simulation cannot provide the detailed flow information,especially flow characteristics along the axial direction,which is unfavorable to improve the performance of positive displacement blower.To investigate the effects of spiral inlet and outlet on the aerodynamic performance of positive displacement blower,three-dimensional unsteady flow characteristics in a three-lobe positive displacement blower with and without the spiral inlet and outlet are simulated by solving Navier-Stokes equations coupled with RNG k-ε turbulent model.In the numerical simulation,the dynamic mesh technique and overset mesh updating method are used.The computational results are compared with the experimental measurements on the variation of flow rate with the outlet pressure to verify the validity of the numerical method presented.The results show that the mass flow rate with the change of pressure is slightly affected by the application of spiral inlet and outlet,but the internal flow state is largely affected.In the exhaust region,the fluctuations of pressure,velocity and temperature as well as the average values of velocity are significantly reduced.This illustrates that the spiral outlet can effectively suppress the fluctuations of pressure,thus reducing reflux shock and energy dissipation.In the intake area,the average value of pressure,velocity and temperature are slightly declined,but the fluctuations of them are significantly reduced,indicating that the spiral inlet plays the role in making the flow more stable.The numerical results obtained reveal the three-dimensional flow characteristics of the positive displacement blower with spiral inlet and outlet,and provide useful reference to improve performance and empirical correction in the noise-reduction design of the positive displacement blowers.
文摘As a new structure of solid matter quasicrystal brings profound new ideas to the traditional condensed matter physics, its elastic equations are more complicated than that of traditional crystal. A contact problem of decagonal two? dimensional quasicrystal material under the action of a rigid flat die is solved satisfactorily by introducing displacement function and using Fourier analysis and dual integral equations theory, and the analytical expressions of stress and displacement fields of the contact problem are achieved. The results show that if the contact displacement is a constant in the contact zone, the vertical contact stress has order -1/2 singularity on the edge of contact zone, which provides the important mechanics parameter for contact deformation of the quasicrystal.
基金the National Natural Science Foundation of China (Nos. 11572289,1171407,11702252,and 11902293)the China Postdoctoral Science Foundation (No. 2019M652563)。
文摘The interface crack problems in the two-dimensional(2D)decagonal quasicrystal(QC)coating are theoretically and numerically investigated with a displacement discontinuity method.The 2D general solution is obtained based on the potential theory.An analogy method is proposed based on the relationship between the general solutions for 2D decagonal and one-dimensional(1D)hexagonal QCs.According to the analogy method,the fundamental solutions of concentrated point phonon displacement discontinuities are obtained on the interface.By using the superposition principle,the hypersingular boundary integral-differential equations in terms of displacement discontinuities are determined for a line interface crack.Further,Green’s functions are found for uniform displacement discontinuities on a line element.The oscillatory singularity near a crack tip is eliminated by adopting the Gaussian distribution to approximate the delta function.The stress intensity factors(SIFs)with ordinary singularity and the energy release rate(ERR)are derived.Finally,a boundary element method is put forward to investigate the effects of different factors on the fracture.
基金the Major State Basic Research Program of China(19990328)NNSF of China(19871051,19972039) the Doctorate Foundation of the State Education Commission
文摘For compressible two-phase displacement problem, a kind of upwind operator splitting finite difference schemes is put forward and make use of operator splitting, of calculus of variations, multiplicative commutation rule of difference operators, decomposition of high order difference operators and prior estimates are adopted. Optimal order estimates in L 2 norm are derived to determine the error, in the approximate solution.
基金supplied by the Japan Aerospace Exploration Agency(JAXA)(Grant Nos.AO-430 and AO-582)supported by National Natural Science Foun-dation of China(Grant Nos.40974006 and 40774003)+2 种基金National Basic Research Program of China(Grant No.2012CB719903)Research Grants Council(RGC)of the Hong Kong Special Administrative Region(Grant No.PolyU5146/11E)Scholarship Award for an Excellent Doctoral Student granted by the Ministry of Education of China(Grant No.085201001)
文摘Differential synthetic aperture radar interferometry (D-InSAR) can only measure one-dimensional surface displacements along the line-of-sight (LOS) direction which greatly inhibits its development and application.In this paper, we introduce a novel approach to measuring two-dimensional (2-D) surface displacements by exploiting a single InSAR pair, which is called multi-aperture InSAR (MAI) technology.We study the effects of baseline errors and the ionosphere on MAI technology and develop a directional filter and interpolator to minimize the ionospheric effects.A PALSAR image pair covering the 2010 Yushu earthquake is used to estimate the 2-D displacement fields of the earthquake using the MAI approach.The experimental results show that MAI is superior to conventional Offset-Tracking and therefore has great potential in co-seismic displacement measurement and source parameter inversion.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51065009)the Science Foundation of Jiangxi Province Education Department of China(Grant No.GJJ14392GJJ14360)
文摘Based on new rolling-sliding compound bearings,the wear between the one-way spiral hollow cylindrical roller and the ribs of the inner and outer ring of rolling-sliding compound bearings is reduced by innovational structural design. A new left-right spiral hollow cylindrical roller is proposed to replace the one-way spiral hollow cylindrical roller. The finite element analysis models of ordinary cylindrical rollers,one-way spiral hollow cylindrical rollers and left-right spiral hollow cylindrical rollers are respectively established by ABAQUS.The axial displacement of their center mass and the stress distribution of left-right spiral hollow cylindrical rollers are compared and analyzed. Theoretical study results show that this new left-right spiral hollow cylindrical roller not only inherits the advantages of one-way spiral hollow cylindrical rollers,but also avoids the axial offset and the serious wear of the one-way spiral hollow cylindrical roller. And the theory research conclusion is verified by the experiment. The left-right spiral hollow cylindrical roller has the advantages to overcome boundary stress concentration like logarithmic convex roller. The rolling-sliding compound bearings equipped with the new rollers can be better to adapt to the impact of vibration load.
